Neuronal specific increase of phosphatidylserine by docosahexaenoic acid.

Phosphatidylserine (PS), the major acidic phospholipid class in eukaryotic biomembranes, plays an important role in various signaling pathways. We have previously demonstrated that docosahexaenoic acid (DHA, 22:6n-3) positively modulates PS biosynthesis and accumulation in neuronal cells, promoting survival. In this paper, we demonstrate that the increase of PS levels upon DHA enrichment is not a universal mechanism, but specific to neuronal cells. When cells were enriched with 20 muM DHA, 18:0, 22:6-PS increased in both neuronal (Neuro 2A) and non-neuronal cells (Chinese hamster ovary K1 cells, NIH-3T3, and human embryonic kidney cells). However, the increase of the total PS level was observed only in Neuro 2A cells because of the fact that other PS species, such as 18:0, 18:1-PS and 18:1, 18:1-PS decreased significantly in non-neuronal cells, compensating for the increase of 18:0, 22:6-PS. DHA enrichment did not affect the messenger RNA levels of PS synthase 1 (PSS1) and PSS2. Over-expression of genes encoding PSS1 or PSS2 altered neither the PS level nor the effect of DHA on PS increase in both neuronal and non-neuronal cells. From these results, it is concluded that the PS increase by DHA, specifically observed in neuronal cells, may represent a unique mechanism for expanding the PS pool so far known in mammalian cells.